Refrigerant compositions



3,37 7,287 Patented Apr. 9, 1968 3,377,287 REFRIGERANT COMPOSITHONS Donovan Erb Kvalnes, Westchester, Pa., and Howard Maurice Parmelee, Woodstowu, N.J., assignors to E. I.

du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware No Drawing. Filed June 4, 1965, Ser. No. 461,511

2 Claims. (Cl. 25267) ABSTRACT OF THE DISCLOSURE Mixtures of 1,1,l-trifluoroethane and chloropentafluoroethane. These mixtures behave like an azeotrope, and they boil in the range of 55 F. to -57 F. They are useful as refrigerant compositions.

This invention relates to refrigerant compositions and more particularly to mixtures of 1,1,1-trifluoroethane and chloropentafiuoroethane which have azeotrope-like characteristics and are useful as low-boiling refrigerants.

The mixed fluorine and chlorine derivatives of methane and ethane have attained widespread use in refrigeration as a result of their low toxicity and chemical inertness and the low specific volumes and range of boiling points possessed by various members of the series. Trichlorofluoromethane [B.P. 74.8 F. (23.8 C.)], dichlorodifiuoromethane [B.P. -21.6 F. (29.8 C.)], chlorodifiuoromethane [B.P. 4l.4 F. (40.8 C.)], 1,2-dichlorotetrafluoroethane [B.P. 38.8. F. (38 C.)], and chloropentafiuorethane [B.P. -37.7 F. (-38.7 represent the most commonly used compounds of this type. Mixtures of some of these compounds in certain proportions are azeotropes.For' Example, Benning, in US. Patent 2,641,579, discloses that a mixture of 49% by weight of chlorodifiuoromethane and 51% by weight of chloropentafluoroethane is an azeotrope having a normal boiling point of 50 F. (45.6 C.) and Lewis, in US. Patent 2,641,580, discloses that a mixture of 84% by Weight of chloropentafluoroethane and 16% by weight of 1,1-difluoroethane is an azeotrope having a normal boiling point of 42.2 F. (4l.3 C.). On the other hand, French Patent 1,320,327 discloses that mixtures of 46% to 69% by weightof difiuoromethane and 54% to 31% by weight of chloropentafluoroethane form two liquid phases having boiling point of about 70.6 F. (57 C.).

An azeotrope is a mixture of two mutually soluble compounds which has a constant boiling point and'a constant distillate composition. The formation of azeotropes cannot be predicted although many attempts have been made to do so. Azeotropes are valuable in many cases because they possess beneficial properties which are not possessed by either of the components of the mixture.

Refrigerants having a wide range of boiling points are needed to allow the design of efficient equipmentfor'various refrigerating demands. The choice of equipment should be made in light of the temperature to be reached, the power cost, the cost of the equipment, and the requirements of space. Increased efliciency of operation and flexibility of design become possible when additional refrigerants of suitable properties are developed.

Although equipment designed to use a particular refrigerant is installed, the need for increased refrigerating capacity sometimes arises. Such a need may be filled with a refrigerant having a lower boiling point and resultant higher vapor pressure at the temperature of the gas before it is compressed and liquefied. It is not practical, however, to use a refrigerant having a boiling point too much lower than that for which a given apparatus has been designed because the power input becomes too high and the compressor motor becomes overloaded. To provide increased refrigerating capacity, for example, for equipment designed for chlorodifluoromethane without excessive change in power input, a gas which is liquefied somewhat below the boiling point of this refrigerant may be used.

It is, therefore, an object of this invention to provide low boiling compositions which are useful as refrigerating agents. Another object is to provide an azeotropic mixture which is effective in low temperature refrigerating installations. A further object is to provide a refrigerant which may be used to give greater refrigerating c pacity with equipment designed for use with chlorodifluoromethane. A still further object is to provide a refrigerant which operates with a smaller temperature ris on compression than chlorodifiuoromethane to ensure against overheating, insulation failure, electrical burnout, and mechanical failure. Other objects are to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accord with this invention by the low-boiling refrigerant l" a a compositlons whlch consist of mixtures of from about 40% to about 75% by weight of 1,l,1-trifluoroethane and from about to about 25% by weight of chloropentafiuoroethane.

It has been found that 1,1,1-trifluoroethane and chloropentafluoroethane form a minimum boiling point azeotrope consisting of 60% by weight of 1,1,1-trifluoroethane and 40% by weight of chloropentafluoroethane having a normal boiling point of 56:l F. (50i0.5 C.), compared with hte normal boiling points of -47.5 C. for 1,1,l-trifiuoroethane and 38.7 C. for chloropentafluoroethane. It has been found further that the mixtures of 40% to by weight of 1,1,1-trifiuoroethane and 60% to 25% by weight of chloropentafiuoroethane have normal boiling points in the range of -55 F. to 57 F. (48.3 C. to 49.5 C.) at a pressure of 14.7 p.i.s.a., which are below the boiling points of the individual components of the mixtures, and that such mixtures hav azeotrope-like characteristics.

The mixtures (compositions) of this invention are very useful as refrigerants and particularly are useful in refrigeration apparatus designed for use with chlorodifluoromethane as the refrigerant when greater refrigeration ca- TABLE I.-CALORIMETER DATA COMPARING THE AZEOTROPE OIIsGFa/CCIFgCFa 60/40 BY WEIGHT AND CHCIF: Condensing Temperature, +110 F.; Return Gas Temperature, +65 F.

Evaporator GH CFsl Temp, F. 0.) cou iers, /40

Compressor Capacity, +20 (-6. 7) 44, 700 B.t.u.,hr. 20 (-28.0) 15,900 -40 (-40) 7,230 Ratio of Compression +20 v90 20 8. 75 -10 13. 70

Compressor Discharge 190 (88) Temp, F. 0.). -20 253 (123) 40 284 (140) Motor Temp, F. C.) +20 115 (46) -20 120 (49) -40 149 (65) CHCIF, Ratio to CHOlFr Difference from lFa From these tests, it will be apparent that the azeotrope is superior in compressor capacity, especially at low evaporator temperatures, and ratio of compression. The azeotrope also exhibits important advantages relative to compressor discharge temperature and motor temperature.

There are only slight changes in the boiling point when the composition is varied over a substantial range on either side of the azeotropic composition. Thus, there is little tendency for fractionation to take place with any of these mixtures and most of the advantages shown in Table I for the azeotro e are retained. Over the composition range of from to 75% by weight of 1,1,1-trifluoroethane and to 25% by weight of chloropentafluoromethane the boiling points of the mixture are lower than that of 1,1,1-trifluoroethane.

In addition to having significant advantages over chlorodifiuoromethane as described, the compositions of this invention can be used in place of the azeotrope of chlorodifluoromethane and chloropentafiuoromethane (a refrigerant now on the market). Compared with this azeotrope, the azeotrope of this invention is slightly superior in having a higher capacity and in having a lower compressor discharge temperature and motor temperature. It has a comparable performance factor. The pertinent data are presented in Table 11.

TABLE II.CALO RIMETE Although 1,1,1-trifluoroethane is flammable, mixtures with chloropentafluoroethane containing 60% and higher amounts by weight of chloropentafiuoroethane are nonflammable in air at room temperature and at 100 C. as determined by the Underwriters Laboratories Test described in their Miscellaneous Hazard Report No. 2375, November 13, 1933, page 97. Furthermore mixtures containing 25% by weight of chloropentafiuoroethane cannot be ignited in air at room temperature. In addition to being nonfiarnmable, the compositions of this invention are chemically inert and essentially noncorrosive. They combine the valuable characteristics possessed generally by fluorochlorohydrocarbons with low boiling point. This combination is of particular significance when low temperatures are to be reached or when additional capacity must be obtained with existing refrigerating equipment.

In preparing these mixtures, it is desirable that the components be at least 99% pure and that they contain no appreciable amount of impurities which are corrosive or which separate upon evaporation. No special mixing procedure need be followed, provided the proper relative amounts of the two components are used.

These refrigerants may be used in domestic and cornmercial refrigerators and freezers, industrial cooling systems and air-conditioning systems, or in any other sys- R DA TA COMPARING THE AZEOTROPE CHsGFa/CClFzCFs 60/40 BY WEIGHT D EH11. AZEOTROPE CHC-lF /CCIFgCFa 49/51 BY WEIGHT Condensing Temperature, +110 F. (43.3 0.); Return Gas Temperature, F. (183C) Evaporator CHsCFz/CClFgCF}, CHClF /CClFzCFz, Ratio to Temp, F. C.) 60/40 49l51 CHClFifCClF CFi Compressor Capacity, B.t.u./hr +20 (-6. 7) 44, 700 42, 250 20 (-28. 9) 15, 000 15, 600 1.02 t- 0) 7, 230 7,000 1.03 Performance Factor, B.t.u./watt +20 7. 10 7110 1.00

hr. 20 3. 4. 10 0. -40 2. 60 2. 60 1- U Difierenoe from CHCiFz/CClFrCFz, F

Cgmprtgssor Discharge Temp, +20 190 88) 195 (90.6) -5 F.( C). 20 253 (123) 266 (130) -13 o 40 284 (140) 302 (I50) 18 Motor Temp, F +20 (46) 107 (42) +8 20 (49) (54) -10 40 158 (70) 9 From Table III, it is apparent that a minimum-boiling .60

azeotrope (i.e., composition having a maximum vapor pressure at any given temperature) exists at about 60% by weight of 1,1,1-trifiuoroethane and 40% by weight of chloropentafluoroethane and that the change in vapor pressure of compositions having between 40% and 75% by weight of 1,1,1-trifiuoroethane is small.

TABLE III.VAPOR PRESSURE, IN LBS/IN. ABSOLUTE, OF GHzOFa/CCIFgCFa COMPOSITIONS IN-PARTS BY WEIGHT Composition '0/100 25175 40/60 60/40 7.5/25 100/0 Temperature, F. 0.):

embodiments so used. On the other hand, it will be apparent to those skilled in the art that, subject to the limitations set forth in the general description, many variations can be made in the proportions of the components in the compositions and in the manner, conditions and apparatus in which they are used Without departing from the spirit or scope of this invention.

From the preceding description, it will be apparent that this invention provides novel low-boiling refrigerant compositions which have azeotrope-like characteristics and which can be considerably varied in composition without loss of those characteristics. They are particularly useful in refrigeration apparatus which has been designed for the use of chlorodifluorornethane to increase the capacity of such apparatus and to provide a number of other advantages. Accordingly, this invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A low-boiling refrigerant composition which consists of a mixture of from about to about 75% by weight of 1,1,1-trifiuoroethane and from about 60% to about 25% by weight of chloropentafluoroethane, said mixture having a normal boiling range of F. to 57 F.

2. A low-boiling refrigerant composition which consists of a mixture of 60% by Weight of 1,1,1-trifiuoroethane and 40% by weight of chloropentafluoroethane, said mixture having a normal boiling point of 56: 1 F.

References Cited UNITED STATES PATENTS 8/1949 Miller et al. 252-67 6/1953 Lewis 25267 UNITED STATES PATENT OFFICE Certificate Patent No. 3,377,287 Patented April 9, 1968 Donovan Erb Kvalnes and Howard Maurice Parmelee Application having been made by Donovan Erb Kvalnes and Howard Maurice Parmelee, the inventors named in the patent above identified, and E. I. du Pont de N emours and Company, Wilmington, Del., a corporation of Delaware, the assignee, for the issuance of a certificate under the provisions of Title 35, Section 256, of the United States Code, deleting the name of Howard Maurice Parmelee as a joint inventor, and a showing and proof of facts satisfying the requirements of the said section having been submitted, it is this 22nd day of December 1970, certified that the name of the said Howard Maurice Parmelee is hereby deleted from the said patent as a joint inventor with the said Donovan Erb Kvalnes.

FRED W. SHERLING Associate Solicitor. 

